Modern mobile communications are tending to provide high speed transmission of multimedia services for users.
FIG. 1 is a schematic diagram illustrating a structure of a system architecture evolution (SAE) system according to the related art.
Referring to FIG. 1, in the system, a user equipment (UE) 101 is a terminal device which receives data. An evolved universal terrestrial radio access network (E-UTRAN) 102 is a wireless access network which includes evolved Node Bs (eNBs)/NBs which provide UEs with interfaces for accessing the wireless network. A mobility management entity (MME) 103 manages mobility context, session context and security information of UEs. A service gateway (SGW) 104 provides user plane functions. The MME 103 and SGW 104 may reside in the same physical entity. A packet data network (PDN) gateway (PGW) 105 implements functions including accounting, lawful interception and so on, and may reside in the same physical entity with SGW 104. A policy and charging rule functions (PCRF) 106 provides quality of service (QoS) policies and charging rules. A serving general packet radio service (GPRS) support node (SGSN) 108 is a network node device providing routing for data transmission in the universal mobile telecommunications system (UMTS). A home subscriber server (HSS) 109 is a home sub system of the UE, and maintains user information including a current location of the UE, the address of the serving node, user security information, packet data context of the UE, and so on.
In long term evolution (LTE) systems of the related art, each cell supports a maximum bandwidth of 20 MHz. LTE-advanced systems adopt carrier convergence to increase peak data rate of UEs. With the carrier convergence technique, a UE may at the same time communicate with multiple cells that are working at different carrier frequencies under the control of one eNB, which provides a maximum transmission bandwidth of 100 MHz, therefore uplink/downlink peak data rate can be increased by several times.
In order to increase the transmission bandwidth, multiple cells may provide service for the same UE. The multiple cells may from the same eNB or from different eNBs. The technique is referred to as carrier aggregation, or dual connectivity.
FIG. 2 is a schematic diagram illustrating a cross-eNB carrier convergence mechanism according to the related art.
Referring to FIG. 2, for a UE working under carrier aggregation, aggregated cells includes a primary cell (PCell) and at least one secondary cell (SCell). There is only one PCell, and the PCell is always activated. The PCell can only be changed through a handover process, and NAS information is only transmitted and received by the UE through the PCell. Physical uplink control channel (PUCCH) can only be transmitted by the PCell. The PCell and the SCell may from different eNBs. The eNB to which the PCell belongs is referred to as a master eNB (MeNB), and the eNB to which the SCell belongs is referred to as a Secondary eNB (SeNB). The MeNB and the SeNB are connected with each other through an X2 interface.
The dual connectivity mechanism provides two manners of establishing bearers. One manner is referred to as split bearer, i.e., a data bearer from the core network to an MeNB is split into two radio bearers which are respectively established on the MeNB and an SeNB. The MeNB performs data splitting, and transmits data packets assigned to the SeNB via the X2 interface to the SeNB. The UE receives downlink data simultaneously from the radio bearers on the MeNB and the SeNB. Regarding downlink data, when an MeNB receives data from the core network, the MeNB performs data encryption, and splits the data packets of packet data convergence protocol (PDCP) so that one part of the data packets are transmitted to the UE via the radio bearer on the MeNB while the other part of the data packets are transmitted to the UE via the radio bearer on the SeNB. The MeNB decides the amount of data packets transmitted respectively by the MeNB and the SeNB, i.e., deciding data packets that are to be transmitted by the MeNB and data packets that are to be transmitted by the SeNB. A properly decided proportion can effectively increase data throughput of the UE. An improper proportion may cause delay in sequencing received data, which reduces data throughput. Therefore, the SeNB is required to report information to the MeNB for the MeNB to decide a proper data split ratio, i.e., deciding the amount of data packets to be transmitted via the SeNB. The information may include the quality of the radio channel between the SeNB and the UE, information about the capacity of available buffer in the SeNB, and the like.
Currently, there is no specification as to whether the capacity of data buffer refers to the capacity allocated for a UE or for a bearer. Buffer of different eNBs may be implemented differently. Some manufacturers produce eNBs that allocate buffer according to UEs, while other manufacturers produce eNBs that allocate buffer according to bearers. Therefore, there is no mechanism that can accommodate the differences of eNBs and provide a flexible manner for reporting the information. The present disclosure provide a method which can better adapt to different implementation manners of eNBs produced by different device providers, effectively use data bearer bandwidth, and reduce data transmission delay.
Therefore, a need exists for a method and an apparatus for assigning data to split bearers in dual connectivity which can better adapt to different implementation manners of eNBs, effectively use data bearer bandwidth, and reduce data transmission delay.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.